1. Field of the Invention
The present invention relates to a mechanism usable for controlling a communication connection with policy control. In particular, the present invention relates to a method of controlling a communication connection with policy control, a corresponding system, a corresponding network control element, a corresponding user equipment and a corresponding computer program product which are usable for a optimizing the resource management, such as a number of active packet data protocol (PDP) contexts, for a communication connection, e.g. between a user equipment and a service providing network, such as a IP Multimedia Subsystem (IMS).
For the purpose of the present invention to be described herein below, it should be noted that                a communication equipment or user equipment may for example be any device by means of which a user may access a communication network; this implies mobile as well as non-mobile devices and networks, independent of the technology platform on which they are based; only as an example, it is noted that communication equipments operated according to principles standardized by the 3rd Generation Partnership Project 3GPP and known for example as UMTS terminals are particularly suitable for being used in connection with the present invention;        although reference was made herein before to multimedia calls, this exemplifies only a specific example of content; content as used in the present invention is intended to mean also multimedia data of at least one of audio data, video data, image data, text data, and meta data descriptive of attributes of the audio, video, image and/or text data, any combination thereof or even, alternatively or additionally, other data such as, as a further example, program code of an application program to be accessed/downloaded;        method steps likely to be implemented as software code portions and being run using a processor at one of the entities described herein below are software code independent and can be specified using any known or future developed programming language;        method steps and/or devices likely to be implemented as hardware components at one of the entities are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS, CMOS, BiCMOS, ECL, TTL, etc, using for example ASIC components or DSP components, as an example;        generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention;        devices or means can be implemented as individual devices or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved.        
2. Related Prior Art
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), and the like are working on standards for telecommunication network and multiple access environments.
In general, the system structure of a communication network is such that one party, e.g. a subscriber's communication equipment or user equipment, such as a mobile station, a mobile phone, a fixed phone, a personal computer (PC), a laptop, a personal digital assistant (PDA) or the like, is connected via transceivers and interfaces, such as an air interface, a wired interface or the like, to an access network subsystem. The access network subsystem controls the communication connection to and from the communication equipment and is connected via an interface to a corresponding core or backbone network subsystem. The core (or backbone) network subsystem switches the data transmitted via the communication connection to a destination party, such as another communication equipment, a service provider (server/proxy), or another communication network. It is to be noted that the core network subsystem may be connected to a plurality of access network subsystems. Depending on the used communication network, the actual network structure may vary, as known for those skilled in the art and defined in respective specifications, for example, for UMTS, GSM and the like.
Generally, for properly establishing and handling a communication connection between network elements such as the communication equipment (or subscriber terminal) and another communication equipment or terminal, a database, a server, etc., one or more intermediate network elements such as network control elements, support nodes or service nodes are involved. Network control elements, such as a Mobile Switching Center (MSC), Service GPRS Support Nodes (SGSN), Gateway GPRS Support Nodes (GGSN) or the like, are responsible for controlling the call establishment, call control, call termination, and the like.
Recently, one major goal in the field of telecommunication is to merge mobile communication networks and the Internet. As a key element for achieving this goal, the IP Multimedia Subsystem (IMS) has been developed that makes it possible to provide access for mobile communication network elements to the services provided by the Internet. Various specifications, for example by 3GPP, are dealing with the architecture and functionality of IMS which are generally known for those skilled in the art.
3GPP provides a mechanism for the network to authorize the establishment of media streams with the IMS. This mechanism is called service based local policy (SBLP) and is specified by 3GPP. In brief, different network entities, such as a GGSN and a Policy Decision Function (PDF), exchange information on authorization and resources for media streams to be established.
According to the current 3GPP specifications, an IMS user equipment using SBLP is required to have at least two active PDP contexts—one for the IMS signalling and one (or more) for the session related media streams. The PDP context used for signalling can be either a general purpose PDP context (i.e. unfiltered) or a signalling PDP context (i.e. filtered so that only IP packets between the UE and pre-defined signalling network elements are passed through, and possibly offering a better QoS). IP packet filters for the media stream PDP context are derived from SDP/SIP (session description protocol/session initiation protocol) and defined by means of packet classifiers by the PDF.
Currently, 3GPP has started working on “3.9G” (3.9 generation), a.k.a. SAE (system architecture evolution) or LTE (long term evolution). The objective of this work is to develop a framework for an evolution or migration of the 3GPP system to a higher-data-rate, lower-latency, packet-optimized system that supports multiple Radio Access Technologies (RAT). Further details of this work are disclosed in the draft technical report 3GPP TR 23.882 V0.9.0. According to this, the basic IP connectivity (“PDP context”) in the evolved architecture is established during the initial access phase of the UE to the network. One aim is that the number of signalling transactions shall be minimized for the set-up of IP connectivity with an enhanced Quality of Service (QoS). Regarding the QoS concepts, it is further specified that for the resource establishment and QoS signalling a preceding signalling of QoS requirements is assumed. This could be either by application signalling (e.g. IMS) or by IP bearer signalling. Moreover, the key issue on QoS concepts encompasses means for providing enhanced QoS for services that require QoS or policies beyond what the default IP access bearer provides.
For the IMS, it is specified, for example in 3GPP specification TS 23.228, V7.2.0, that the UE can use a single general purpose PDP context for both the signalling and the media streams of an IMS session. However, in such a case, there are no signalling filters nor SBLP based packet classifier filters provided, which means that the SBLP cannot actually be used and all traffic (including spam) may pass through. Alternatively, it is specified that the UE can use a general purpose PDP context for the signalling and a separate PDP context with SBLP based filters for the media streams of an IMS session. Thus, as mentioned before, there are two PDP contexts at the least. Furthermore, there are no signalling filters provided, i.e. all traffic (including spam) may pass through. As a further alternative, the UE can use a signalling PDP context for the signalling and a separate PDP context with SBLP, based filters for the media streams of an IMS session. Hence, again two PDP contexts at the least are required.
In a change request (CR) for the 3GPP specification TR23.207 V6.3.0 dated August 2004, it is proposed that the UE is enabled to activate/modify at least one non-realtime PDP Context on each Access Point Name (APN) (with UMTS traffic class background or interactive) without including a Media Authorization Token to a corresponding activation/modification message. However, this proposal does not provide any details or suggestions regarding the problem how to apply filtering.
Therefore, according to the current specifications, for example by 3GPP, a UE communicating with the IMS by using SBLP has to have at least two active PDP contexts—one for the IMS signalling and one (or more) for the session related media streams. The PDP context used for signalling can be either a general purpose PDP context (i.e. unfiltered) or a signalling PDP context (i.e. filtered so that only IP packets between the UE and pre-defined signalling network elements are passed through, and possibly offering a better QoS).